Ferberite, Marcasite
Tazna Mine (Tasna Mine; Tazna-Rosario Mine), Cerro Tazna, Atocha-Quechisla District, Nor Chichas Province, Potosi Department, Bolivia
Cabinet, 9.6 x 6.6 x 5.1 cm
A very heavy, multi-twinned crystal of Ferberite from the Tazna mine in southern Bolivia. The piece was mined at the beginning of 2008, which is encouraging because I have seen very little in the way of Ferberites from this mine in recent years. This piece features the classic, "butterfly" twinning of Ferberite along the a (100) face. It is a fine, sharp, very large jet-black twinned crystal with associated botryoidal Marcasite (on the back; second photo). It has an attractive thick blocky form. Twinned crystals from Bolivia are becoming increasingly difficult to obtain in recent years as the price of Tungsten ore has driven the miners to throw nearly all the Ferberite into the crusher, causing thousands of specimens to be lost forever. These twins are definitely the most highly sought after crystal habit from this locality.